1. Field of the Invention
This invention relates to improving the performance of two or more pressure compensated pumps, with or without load sensing, that supply fluid to a single driven circuit. The invention uses a rotary type flow divider operating in reverse to make fluid flow through the pumps at the same rate of flow even when the pumps are limited to different output pressures.
2. Background Information
It is often necessary to use more than one pressure compensated pump, with or without load sensing, to supply a hydraulic circuit's highest flow demand. A prior art hydraulic system might use separate pumps, with separate drive motors for each pump, to feed into a common manifold that supplies pressurized hydraulic fluid to a circuit. In such a prior art arrangement there is an attempt to set each pump so that they will operate at the same sensed pressure level such that when there is a need for pressurized flow that both pumps will supply at least part of the flow. The main problem with such a prior art arrangement is that no matter how closely the pumps are set, one pump will almost always start first and the other pump or pumps sensing the increased pressure will not operate. Even when it is possible to set the pumps to supply flow simultaneously, contamination, wear, spring deterioration and other variations will soon change such that one pump will start off supplying flow and the other pump or pumps will not start until the system requirements exceed the capacity of the first pump. The concept can be implemented with two or more pumps.
The prior art multiple pump system allows one pump to lead and the other pumps to start flowing when pressure drops due to a flow demand higher than the first pump can supply. One pump starts and the others start as needed. Some pump manufacturers recommend their pumps be set with triggering pressures 100–150 PSI apart so that they will not try to start flowing at the same time. The problem with starting the prior art system pumps at nearly the same pressure is that the first pump can be forced to no flow when the second pump flow reaches the manifold. In this situation the pumps can oscillate on and off so fast that they suffer mechanical damage.
Thus it can be seen that there is a need for a multi-pump system that will allow for multiple pumps to supply hydraulic fluid to a single hydraulic circuit.